Underpinning

[svouts]

Hello,

I have a garden boundary wall that is double brick 7 feet tall and 15 feet long. It has signs of subsistence. I have repaired a few cracks the last two years but there are more developing in the middle section. On one side it is attached to the house. It looks that it seats on the soil with no foundations. I want to support it with underpinning.

What is the best way for underpinning the wall, any practical hints?

Can I do underpinning only in middle 4-5 feet of the length under were the cracks appear?

 

[theprinceofdarkness]

I have just under pinned about 40' of a two storey stone barn. The way to do is to first of all work out what you want to do, i.e. how deep, how wide, right under the wall or to one side. . .. Do it in short sections, I would say a foot long and a yard apart. what I did was to dig my hole up against the wall, to the right depth, then dig it under the wall. Put in a layer of stiff mortar, place concrete block flatwards in hole under wall. Beat it down tight. Mix up some sharp sand mortar put some on the block and on the top of the brick, push it in hard and pack out the mortar so its tight under the wall on on the block. Go away and do another one come back to do an adjacent slot three days later.
I start away from the cracked bit and sort of work towards it, so the wall is either being supported on the old or new foundations before you disturb the dodgy bit.
If you can get to both sides I would have two high density blocks as the foundation "stone" and at least one brick under the wall so when the earth is put back, your repair will be invisible. It wwould be super to be able to lay the new foundation as one strip. Just leave a side gap (1/2"?) between the blocks and fill with rich mortar hen you do the adjacent section.
Frank

 

[^woody^]

I would say a foot long and a yard apart.

And what if the OP has other things to do before 2023?

1 metre lengths is the convention

 

[^woody^]

It has signs of subsistence

And what are the signs?

 

[kazuya]

i did a number of bungalows for the council, engineer said 1 meter sections, and i also had to knock rebar half way into the sides before filling with concrete, it does make it difficult to dig the other sections out, but obviously it joins the sections and its much stronger

 

[theprinceofdarkness]

2023 ?, four days. No chance of the dodgy wall falling over/sinking more.
Frank

 

[themiddleagedun]

2023 ?, four days. No chance of the dodgy wall falling over/sinking more.
Frank

I think he was exaggerating to make a point? Funny though.